The present invention relates generally to blood pressure evaluation procedures and more particularly to a non-invasive, oscillometric technique for determining certain information associated with blood pressure, specifically its mean pressure and blood pressure constant.
In applicant's copending patent application Ser. No. 684,592, filed Dec. 21, 1984, now abandoned incorporated herein by reference, there was described a non-invasive, oscillometric technique for generating a waveform (FIG. 7 of the copending application) which approximates the actual blood pressure waveform of a given mammal (hereinafter referred to as the patient or subject). The copending application also described non-invasive techniques for obtaining the diastolic and systolic pressures of a patient. The copending application further described a technique for utilizing this information, that is, the approximated blood pressure waveform, and the diastolic and systolic pressures, to approximate the patient's mean blood pressure and blood pressure constant. More specifically, as discussed in detail in the copending application, the mean pressure P.sub.b (M) of the approximated blood pressure waveform is equal to the diastolic blood pressure P.sub.b (D) of the subject plus a particular fraction Kb (the blood pressure constant) of the difference between the patient's systolic blood pressure P.sub.b (S) and his diastolic blood pressure P.sub.b (D). Equation 1 below shows this. EQU P.sub.b (M)=P.sub.b (D)+K.sub.b (P.sub.b (S)-P.sub.b (D)) 1
Note that the mean pressure P.sub.b (M) can be calculated by integrating the waveform (its pressure amplitude P.sub.b) over its period T (the duration of the waveform) so that: ##EQU1## We can also define all of the above in terms of the equivalents analogous quantities found from our measurement of the non-invasive cuff pulses.
Thus we have the analogous minimum and maximum cuff pulse pressures P.sub.c (D) and P.sub.c (S) respectively and the analogous cuff means pressure and cuff pressure constant P.sub.c (M) and K.sub.c. The equations analogous to 1, 2 and 3 above are: EQU P.sub.c (M)=P.sub.c (D)+K.sub.c (P.sub.c (S)-P.sub.c (M)) 4 ##EQU2## With the above equations in mind, the mean blood pressure value P.sub.b (M) and the blood pressure constant K.sub.b can be determined non-invasively by first generating again, non-invasively, a cuff waveform which approximates the subject's actual blood pressure waveform and determining the subject's diastolic and systolic cuff and blood pressure, as described in the copending application.